Three weeks ago, it looked like David Letterman was going to make it his top priority to get Barack Obama elected after Republican Presidential nominee John McCain bailed at the last minute on a scheduled Late Show appearance, claiming he had to return to Washington, DC, only to appear on a morning talk show in NYC the next morning.

But any bad blood was put to the side on Thursday night when McCain finally made a belated trip to the CBS show.

"I screwed up," McCain admitted to Dave and his audience. "But look at all the conversation I gave you."

Preparing for the onslaught of tough questions, he joked, "I have a son in the Marine Corps and I asked him to FedEx his helmet and flack jacket, but it didn’t get here in time."

Despite the lightheartedness of the exchange, Letterman maintained a strong line of questioning, probing McCain on everything from his running mate, Sarah Palin, to the Republican campaign line that Obama has "palled around with terrorists."

"Are they double-dating, are they going to dinner, what are they doing?" Letterman asked about the implied connection between Obama and William Ayers. "Are they driving across country?"

"Maybe going to Denny’s," McCain said.

Turning the tables on the Arizona Senator, Letterman asked, "Did you not have a relationship with [convicted Watergate burglar] Gordon Liddy?"